1. Field of the Invention
This invention relates to a charge image recording medium.
2. Description of the Prior Art
In recent years, a number of imaging devices based on a process using the latent image of electron-charge have been proposed that offer the hope of practical usefulness in image picking-up, image recording, image reproducing and image displaying. An example of such devices is disclosed in U.S. Pat. application Ser. No. 301,324 (filed on Jan. 24, 1989, a C.I.P. of U.S. Ser. No. 139,005), in which an optical image inputted is converted to a latent image of electron-charge, recorded on a recording medium and reproduced. The mechanisms for recording and reproducing, and an example of media proposed in this reference, are illustrated in FIGS. 8, 9 and 5, respectively.
A writing head WH or a reading head RH are necessary for operating the recording and reproducing of a charge image by the use of a charge image recording medium, as will be described later in detail with reference to FIGS. 8 and 9. Use of a light-modulation material at the part having the function of retaining a charge image in a charge image recording medium RM (i.e., a dielectric layer IL in the charge image recording medium RM illustrated in FIGS. 6 and 9) makes a reading head unnecessary at the time of reading. Hence, a recording medium comprising a lamination of an electrode and a layer (a light-modulation material layer) comprised of a light-modulation material is often used as the charge image recording medium RM.
However, since a recording medium may have a great variety of forms as exemplified by a tape, a disk, a sheet and a card, it has not been easy to construct the light-modulation material layer on the charge image recording medium that may have various forms. In particular, it has been difficult to construct the light-modulation material layer on a charge image recording medium having a large area or a charge image recording medium having the form of a tape.
The above difficulty also applies in the case when the light-modulation material used in constituting a light-modulation material layer comprises, for example, a liquid crystal or lithium niobate.
When the part at which a charge image is recorded is constituted of a dielectric layer IL, a charge image can be well recorded in a highly detailed state. In a conventional charge image recording medium RM, however, the charges of a charge image recorded thereon may gradually decrease with lapse of time and it has occurred even that the charge image can be retained only for several hours to several days or so. Thus, it has been sought to provide a charge image recording medium capable of storing a charge image for a long period of time.